The invention relates to a tube separator for use in particular in water lines to shut-off the water line.
Such a tube separator is disclosed in German Patent Specification 32 47 325. The function of this known tube separator is based on a pressure comparison between the inlet side and the outlet side of the tube separator; in dependence on the pressure conditions a tube separator piston or a piston separator tube changes position by the action of the water pressure into an open position or for separation by action of the inlet pressure drop through a spring which directly acts upon the tube separator piston or on the piston separator tube into the shut-off or respective operating position. This requires relatively large displacements of the piston into the respective end positions. Further, the sliding surfaces must be of good quality in order to ensure the tightness between the tube separator piston and the tube separator housing. The continuous exchange of pressure water at the tube separator leads to deposits on the sliding surfaces in the piston chamber which will cause wear of the seal members. Moreover, relatively large springs are required for lifting the tube separator piston back up. If this restoring spring does not operate properly, the tube separator piston can not be switched back into the shut-off position.
The german Utility Model 98 05 206 discloses a tube separator which consists of two conventional check valves and two modified conventional backflow preventing devices arranged between the check valves in a cross piece vertically above each other. The essential element of the upper backflow preventer is a ball which is pressed into a valve seat by the pressure of the water flowing through the tube separator in the open position thereof and which drops off from the valve seat on interruption of the flow. This upper backflow preventer functions to vent the cross piece in the shut-off position. The lower backflow preventer comprises a ball which is pressed by the action of the passing water onto a valve seat against a spring force and pressed away from the valve seat by the spring on termination of the flow. This lower backflow preventer serves to drain water from the cross piece is the shut-off position. This known tube separator does not meet the actual legal requirements regarding the safety of operation; further, its function is very sensitive to the proper position of the balls in the valve seat which can easily be affected e.g. by pollutions or deposits.